Abstract

Extreme seasonal variation of water level is observed in many aquatic systems in the south of the Iberian Peninsula. During dry periods, crayfish are subject to more or less extreme environmental conditions, particularly in the shrinking pools with high temperatures and low water quality. Procambarus clarkii have adapted to these alternating wet and dry conditions and in summer individuals burrow to avoid desiccation and to reproduce. Because of the lack of information on the burrowing behaviour of Procambarus clarkii and its trophic activity, a study on these aspects was undertaken. Average burrow density, burrow occupation and diet of burrowed crayfish were studied in a small reservoir in the south of Portugal during the summer period. Average burrow density ranged from 0.28/m² to 0.48/m² and most of the animals in the burrows were mature. Most burrows were occupied by a male and a female with or without eggs. Three types of burrow condition were observed: (i) opened and with fresh material at the entrance; (ii) closed with a fresh chimney and (iii) closed with a very dry chimney. Digestive fullness correlated positively with the freshness of the burrow entrance indicating some feeding activity in the exterior during the burrowing period. Crayfish diet was mainly composed of macro-invertebrates and detritus.

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